Carbon dioxide lasers for otosclerosis

Abstract

Over the past eight years, the senior author (SGL) has sought the ideal microsurgical laser for otosclerosis surgery. This quest required learning the principles of laser physics and of the interactions of light with matter. Rather simple thermocouple experiments were performed in the laboratories of the Midwest Ear Foundation (MEF) to confirm some of what was predicted from these principles. More sophisticated transmission spectroscopy experiments were performed at the Massachusetts Institute of Technology (MIT) to evaluate which electromagnetic wavelengths are best absorbed by collagen and bone. MIT's spectroscopy studies paralleled MEF's thermocouple data. CO2 laser energy (10.6 microns) is nearly completely absorbed by collagen and bone, whereas visible argon and KTP laser energy (0.5 micron) is poorly absorbed. Despite the better optical precision of visible lasers, the author chose the CO2 laser for stapedectomy revision and stapedotomy, because long infrared electromagnetic energy has vastly superior tissue absorption characteristics for these procedures. With the development of I. L. Med's Unilase, the otologic surgeon now has a CO2 laser with optical precision and convenience approaching that of visible lasers. Clinical studies of 102 consecutive CO2 laser stapedectomy revisions show that in 92% of patients, hearing was significantly improved with the new CO2 laser revision techniques. Nearly half of these patients had undergone one or more previous, unsuccessful, nonlaser revisions. For primary otosclerosis, CO2 laser stapedotomy has simplified a technically difficult operation while significantly reducing mechanical trauma to the inner ear. Most gratifying to the senior author is that after approximately 450 consecutive CO2 laser operations for otosclerosis, no patient has experienced significant postoperative sensorineural hearing loss (greater than 15 dB; mean 500, 1000, 2000, 3000 Hz). This fact alone has justified our theoretical and laboratory efforts to find the safest laser for otosclerosis surgery.